Rockbox mail archive
Subject: AW: AW: AW: Still Problems with AJB Remote
From: Matthias Klumpp (Matthias.Klumpp_at_gmx.de)
Date: 2004-07-13
Hi Jörg,
many thanks for your help (please have another short look below).
# -----Ursprüngliche Nachricht-----
# The "circuit" is very simple: connect the source to the Archos, drain to
# your TTL input/output, gate to a 3.3V reference. The transistor draws no
# power from there, it's just a reference. However you do this, maybe a
# voltage divider from 5V. (eg, 22kOhm towards ground and 12 kOhm towards 5V
# will give 3.2V at the midpoint)
#
# If your Archos needs an external pullup, you can connect it via maybe
# 4.7kOhm to 5V. This is safe, the pin is capable to limit the voltage if
the
# current is limited by such a resistor.
#
# I'm no good in ASCII drawing, but I hope it's understandable without.
So I'll do it, just to be sure:
+5V
|
+-------------------------------+
| |
+-+ +-+
| |22k | |4.7k
| | | |
+-+ +-+
+---------------------+ |
+-+ | |
| |12k | |
| | | |
+-+ | |
| | |
| | |
--- | |
|G |
------ |
D| |S |
uC Out port--------+ +--------+-- AJB remote
Like this ?
I would like to have a "universal" circuit, that works with both (AJB with
and without internal pull-ups).
Does this schematic work both ways or do I have to take out the 4.7k, if I
already have the pull-up inside the AJB ?
Gruß / Regards / Abraço
Matthias
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